Unit 5: States of Matter

Content Outline: Solids (5.2)

  1. There are 2 types of solids based upon atom/molecule arrangement within the solid.
  1. Crystalline Solids (Crystals)
  1. These substances possess atoms/molecules that are arranged in a repeating,orderly, geometric pattern.

For example: diamonds, rubies, emeralds, quartz, and salts

  1. The types of crystals based on geometric patterns (a.k.a. lattices) are:
  1. Cubic (Has equal dimensional sides)
  2. Hexagonal (Looks like a 3-D Stop sign, but with six sides)
  3. Orthorhombic(an elongated rectangular rectangle with rectangular, angled ends)
  4. Monoclinic (Small Diamond…almost cubic)
  5. Tetragonal (Elongated rectangle with square ends)
  6. Triclinic (Tilted rectangle with pointed ends)
  7. Trigonal (Diamond shaped cube with pointed ends)
  1. Amorphous Solids (“a” means “without”; “Morph” means “shape”)
  1. These substances possess atoms/molecules that are randomly arranged.

For example: glass, lava, and plastics

  1. Kinetic Theory of Matter Characteristics
  1. Expansion (can atoms/molecules “expand” their given “space”)
  1. Solids generally cannot expand without a change in energy (heat or cooling).
  2. Solids have definite shapes without a container.
  3. Solids have definite volumes.
  1. Fluidity (the easeof movement past one atom/molecule by another because of attractive forces between atoms/molecules)
  1. Solids possess atoms/molecules that are not fluid (able to move).
  1. Solids atoms/molecules vibrate in a fixed position.
  2. This inability to “move” is directly related to the strong intermolecular attractive forces between atoms/molecules.
  1. Intermolecular Attractive (Binding)forces of Crystals
  1. Covalent Network(Examples Diamonds or Quartz –SiO2)

i. There are only very strong covalent bonds between all atoms/molecules.

ii. These are extremely hard substances; but brittle - able to be fractured into smaller

pieces.

iii. Have very highmelting and boiling points.

  • Melting – going from solid to liquid with absorbing energy (heat)
  • Boiling – going from liquid to gas with absorbing energy (heat)
  • Freezing – going from liquid to solid with loss of energy (heat)
  • Condensation – going from gas to liquid with loss of energy (heat)
  1. Covalent Polar Molecule(For example: Ice)

i. Individual molecules possess polar covalent bonds.

ii. The polarity of the individual molecules allows for the attraction between molecules by

London Dispersion Forces (a.k.a. Van der Waals Interactions), Dipole – Dipole

Interactions, or Hydrogen Bonds.

iii. These tend to be very soft (flexible)crystals.

iv. These tend to have low (negative) melting and boiling points.

α. The low melting and boiling points are due to the very weak intermolecular

attractive forces between individual molecules.

  1. Covalent Non-polar Molecules (Examples: solid Oxygen, solid Hydrogen, solid Methane- CH4)

i. Individual molecules possess non-polar covalent bonds.

ii. Each individual molecule is “held” to other molecules by very weak London Dispersion

Forces (a.k.a. Van der Waals Interactions).

iii. These are extremely soft crystals.

iv. They have extremely low melting and boiling points

α. The extremely low melting and boiling points are due to the very weak

intermolecular attractive forces between individual molecules.

  1. Ionic Crystals(Example: Salt)

i. These crystals are composed of positively charged ions that are strongly attracted to

negatively charged ions in an alternating pattern.

α. Positive Ions (Cations) – metals from Groups 1 or 2.

β. Negative Ions (Anions) – non-metals from Groups 16 or 17.

ii. They are hard solids, but very brittle.

iii. They have high melting and boiling points.

α. The high melting and boiling points are due to the very strong

intermolecular attractive forces between individual ions.

  1. Metallic Crystals (Examples: Copper wire, aluminum cooking pan, iron pan)

i. These solids are composed of individual metal cationssurrounded by a “sea of

delocalized(flowing) negatively charged electrons.

α. The delocalized (flowing) electrons make these solids great conductors of

electricity and heat. Remember that electrons possess Kinetic Energy as they are

orbiting the atoms nucleus.

ii. They have very high melting and boiling points, hence why we can cook with them.

α. The high melting and boiling points are due to the very strong

intermolecular attractive forces between individual ions.

  1. Attractive (Binding) Forces of Amorphous Solids
  1. These solids are held together by a variety of combined intermolecular forces.

i. Due to this combination of attractive forces, these solids do not have defined melting or

boiling points.

ii. This is because they are composed of various different atoms/molecules.

iii. These can sometimes be classified as supercooled liquids.

α. These substances look solid, but can flow.

(Examples: lava, molten steel, molten glass)

  1. Density (how compact/close are the atoms/molecules to each other)
  1. Solids generally have very high densities due to the atoms/molecules being very compact already due to the intermolecular attractive forces. (See above in B.)
  1. Compressibility (can the atoms/molecules be moved closer to each other)
  1. Solids are generally notcompressible do to the high density of the atoms/molecules.
  1. There exists very little vacant space between the atoms/molecules.
  1. Diffusion (the ability of atoms/molecules to “mix” together over time)

1. Some slight diffusion may occur, but rarely does, and is extremely slow.